1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel capable of improving its brightness and a method of fabricating the same.
2. Description of the Related Art
Generally, a plasma display panel(PDP) radiates a fluorescent material by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP permits it to be easily made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current(DC) driving system and an alternating current(AC) driving system.
The PDP of AC driving system is expected to be highlighted into a future display device because it has advantages in the low voltage drive and a prolonged life in comparison to the PDP of DC driving system. Also, the PDP of alternating current driving system allows an alternating voltage signal to be applied between electrodes, which dielectric layers are intervened between, to generate a discharge every half-period of the signal, thereby displaying a picture. Since such an AC type PDP adapts a dielectric material which surface accumulate a wall charge during the discharge, a memory effect is produced.
Referring to FIG. 1, there is shown a PDP of AC driving system that includes an upper plate 20 and a lower plate 22. The upper plate 20 consists of a sustaining electrode pair 6 arranged, in parallel, on an upper glass substrate 2, a bus electrode pair 10 installed in each of the sustaining electrode pair 6, a dielectric layer 14 formed on the surfaces of the bus electrode pair 10 and the upper glass substrate 2, and a protective layer 16 formed on the dielectric layer 14. The sustain electrode pair 6 is made from a transparent metal material (e.g., indium tin oxide), and which allows a surface discharge to be maintained successively during a sustaining period. Generally, the sustaining electrode pair 6 is formed on the upper glass substrate 2 by the screen printing technique. The bus electrode pair 10 is responsible for reducing an electrical resistance of the sustaining electrode pair 6. The bus electrode pair 10 is formed on each of the sustaining electrode pairs 6 by vapor-depositing Cr/Cu/Cr and thereafter etching the same. The dielectric layer 14 is accumulated with electric charges generated during the discharge. The dielectric layer 14 is formed on the sustaining electrode pair 6 and the upper glass substrate 2 by the screen printing technique. The protective layer 16 is responsible for protecting the dielectric layer 14 from a sputtering due to the discharge. The protective layer 16 is grown on the dielectric layer 14 with MgO with a thickness of about 2000 .ANG.. FIG. 2 shows a plane arrangement state of the upper plate 22.
The lower plate 22 includes address electrodes 8 provided on a lower glass substrate 4 in such a manner to be perpendicularly crossed with the sustaining electrode pair 6, a barrier rib 12 extended perpendicularly from the surface of the lower glass substrate 4 with positioning the address electrodes 8 therebetween, and fluorescent bodies 18R, 18G and 18B coated on the barrier rib 12 and the lower glass substrate 4. The address electrode 8 allows an opposite discharge to be generated along with one sustaining electrode in the sustaining electrode pair 6 during an address period to thereby select discharge cells being displayed. The address electrode 8 is formed on the lower glass substrate 4 by the screen printing technique. The barrier rib 12 provides a discharge space of the discharge cell along with the upper and lower glass substrates 2 and 4 to shut out an electrical and optical interference between the discharge cells. The barrier rib 12 is formed in such a manner to be perpendicularly extended from the lower glass substrate 4 by the screen printing technique or the sand blast technique. The fluorescent bodies 18R, 18G and 18B is excited by an ultraviolet generated during the discharge and then transited, thereby generating an intrinsic color of visible light.
After bonding the upper plate 20 to the lower plate 22 and evacuating a residual air within a discharge space in the discharge cell between the upper plate 20 and the lower plate 22, an discharging gas such as He+Xe or Ne+Xe is injected into the discharge space in the discharge cell with an appropriate pressure through the injection hole. Then, the injection hole is sealed such that the discharge cell has an airtight structure, thereby completing a PDP of AC driving system.
The radiation in the PDP of AC driving system allows an opposite discharge to be generated at a part of discharge cells in the address interval, and allows each discharge cell generating the opposite discharge to perform a surface discharge in the sustaining interval, thereby displaying a picture. More specifically, if a voltage is applied to a single sustaining electrode of the sustaining electrode pair 6 and to the address electrode 8, then the opposite discharge is generated between the sustaining electrode 6 and the address electrode 8 by a voltage difference. An ultraviolet generated by the address discharge excites and transits the fluorescent bodies 18R, 18G and 18B. At this time, the fluorescent bodies 18R, 18G and 18B generates a visible light. The sustaining electrode pair 6 generates a surface discharge by a sustaining pulse applied in the sustaining interval to maintain the radiation of the fluorescent bodies 18R, 18G and 18B.
As shown in FIG. 3, a discharge generated in the course of the sustaining interval is enlarged from the nearest part to the sustaining electrode pair 6(i.e., a part in which the discharge radius R is minimum) into the distant part thereto(i.e., a part in which the discharge radius R is large) as a sustaining discharge time elapses. At this time, an intensity of electric field becomes largest at the part having a minimum discharge radius R. Accordingly, the density of electron and ion is highest at the surface of the protective layer 16 in which electrons and ions with a high temperature and energy exist mostly. Since a quantity of ultraviolet applied to the fluorescent bodies 18R, 18G Dan 18B becomes larger as the density of electron and ion becomes higher, the brightness increases. On the contrary, since a quantity of ultraviolet becomes smaller as the density of electron and ion becomes lower, the brightness decreases.
In the conventional AC driving system PDP, the brightness is raised by heightening a level of the sustaining pulse to heighten the density of electrons and ions generated during the discharge. However, it is difficult to obtain a brightness at the satisfiable level even when the sustaining voltage is raised. Also, a consumption power of the PDP is increased as the sustaining voltage becomes high. Accordingly, a scheme capable of obtaining a sufficient brightness is required for the AC driving system PDP.